Hamon (swordsmithing)

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Hamon" swordsmithing – news · newspapers · books · scholar · JSTOR (March 2008) (Learn how and when to remove this message)

In swordsmithing, hamon (刃文) (from Japanese, literally "edge pattern") is a visible effect created on the blade by the hardening process. The hamon is the outline of the hardened zone (yakiba) which contains the cutting edge (ha). Blades made in this manner are known as differentially hardened, with a harder cutting edge than spine (mune) (for example: spine 40 HRC vs edge 58 HRC). This difference in hardness results from clay being applied on the blade (tsuchioki) prior to the cooling process (quenching). Less or no clay allows the edge to cool faster, making it harder but more brittle, while more clay allows the center (hira) and spine to cool slower, thus retaining its resilience.^[1]

Hamon does not refer to the white area on the side of the blade. The white part is the part that is whitened by a polishing process called hadori to make it easier to see the hamon, and the actual hamon is a fuzzy line within the white part. The actual line of the hamon can be seen by holding the sword in your hand and looking at it while changing the angle of the light shining on the blade.^[2][3]

Hamons were developed by and traditionally found in Japanese swordsmithing. Similar features are often found in knives and swords from the West and are sometimes called temper lines, although these are not often produced with clay but by other means such as partial quenching, flame hardening, or differential tempering, which produces many differences from a traditional hamon. A true hamon, and many of its key features such as a nioi, have no direct translation into English, thus the Japanese terms are usually used when referring to clay-quenched blades.^[4]